Lubricating oil



vvul bll lluul zoo-52a Patented June 8, 1937 XS'DQ ($15 UNITED STATESPATENT OFFICE Kenneth Taylor, Chicago, Ill., and Bernard H. Shoemaker,Hammond, Ind., assignors to Standard Oil Company, Chicago,-lll., acorporation of Indiana No Drawing. Application February 23, 1933, SerialNo. 658,150

1 Claim. (Cl. 196-13) This invention relates to a method of treatingmineral lubricating oils and it pertains more particularly to the art ofpreparing lubricating oils stable to oxidation and sludging.

5 Petroleum is essentially a mixture of hydrocarbons comprising severalgroups or homologous series of compounds, such as the paraiiins,hydroaromatics, aromatics, polymethylenes, and various other series ofcompounds in which the hyviscosity index", as used herein, refersspecifically to the index defined by Dean and Davis in Chemical andMetallurgical Engineering, vol. 36, 1929, page 618. The viscosity indexof a labricating oil is an indication of its composition or type, i. e.,whether it is a paraffin base or naphthene base oil. Paraflin base oilsare arbitrarily assigned a viscosity index of 100, naphthene base oilsare assigned a viscosity index of drogen to carbon ratio varies to awide degree. 0, and mixed base oils lie between these extremes. 10

A large number of individual compounds of each For example, if an oilshows a viscosity index of series are present and have different boilingabout 85 to 90, it is evident that the oil is prepoints, physical andchemical properties. In the dorninately paraflinic in nature. varioustypes of crude petroleum commonly One of the common ways of increasingthe known as paraflin base, naphthene or asphalt paraflinic content of alubricating oil is to treat 15 base, and mixed base oils, these variousseries the oil with fuming sulfuric acid. The oil and of hydrocarbonsare present in different proporacid are mixed and agitated in theproportion of tions. For example, in paramn base oils, such about one totwo pounds of fuming acid for each as those from the Appalachian field,there is a gallon of oil. The mixture is then allowed to relatively highproportion of parafiinic hydrosettle and the acid layer, comprisingsulfuric acid 20 carbons having a chain structure and a high hyand acidsludge, settles to the bottom and is drogen to carbon ratio, whereas inthe California drawn off. The top layer comprises an oil which and GulfCoastal oils there is a high proportion is high in parafiinic compounds.Also, lubricatof naphthenic hydrocarbons and hydrocarbons ing oilrefined in this way contains a relatively with ring structures and lowhydrogen to carbon large quantity of sulfonic compounds which must 25ratio. The mixed base oils, such as those from be removed before the oilcan be satisfactorily Oklahoma and the Mid-Continent area, are in usedfor most lubricating purposes, and this opgeneral intermediate betweenthese extreme eration is often expensive and wasteful because typ oftroublesome emulsions which are encountered.

In normal refining of crude petroleum, the The quality of the acidtreated lubricating oil 30 fractions of varying distillation rangeswhich are can be fairly judged from two of its properties, successivelyobtained by distillation of the oils that is, the viscosity index andstability against partake of the general character of the crude; sludgeformation. The sludge stability is deterfor example, lubricating oilsderived from Apmined by bubbling air at the rate of 10 liters perpalachian crudes will show parafiinic characterhour into a 250 cc.sample of oil at 340 F. Sam- 35 istics, whereas the lubricating oilsderived from ples of 10 grams each are withdrawn at inter- Gulf Coastaloils show naphthenic characterisvals and tested to determine the amountof sludge tics. The distillates from the mixed base crudes, formed foreach 10 grams of oil. When the such as those from the Mid-Continentarea, will amount of sludge has increased to 10 mg., the

40 show characteristics common to both the naphnumber of hours ofoxidation is noted and the 4 thenic and parafiinic oils. An importantpropsludge stability of the oil is then expressed in erty of parafliniclubricating oils is their low vishours required to form 10 mg. of sludgeper ten cosity temperature coefficient or rate of change grams of oil.The amount of sludge is deterof viscosity with temperature. Thisproperty mined by diluting the 10 gram sample of oil with makes themparticularly suitable for certain luprecipitation naphtha, filtering offthe precipita- 45 brication problemswhere high temperatures are tionnaphtha insoluble residue, and then washencountered. At low temperaturesalso, these ing the filter repeatedly with precipitation naphoils retaintheir fluidity better, an important contha-the residue being sludge.sideration in cold weather operation of automo- Another method ofincreasing the paraflinic biles, for example. For this reason it is veryhydrocarbon content of lubricating oils, as ex- 50 desirable to separatethe mixed base oils into emplified by the viscosity index, is to extractthe their paraffinic constituents and non-paraffinic oil, preferably adewaxed oil, with an organic sol- .constituents. vent such aschlorinated ethers, sulfur dioxide,

The parafiinic characteristics of an oil may be chlorohydrins, mixturesof nitro-benzene and x sed by its viscos ty ndex. The expressionacetone, sulfur dioxide, and benzene and the 55 like. These solventshave a preferential solubility for the naphthenic constituents of theoil and are capable of separating a mixed base oil into two majorfractions. They are the paraffinic fraction of hydrocarbons and thenaphthenic fraction of hydrocarbons. These extraction processes areusually carried out by mixing 2 to 5 parts of solvent with about 1 to 2parts of oil and then heating and agitating the mixture untilsubstantially complete miscibility is obtained. The mixture is thenpermitted to cool and stratify. The major portion of the solvent andnaphthenic aromatic and aromatic-like compounds and hydrocarbons settleto the bottom and the paraffinic portion of the oil segregates into thetop layer and is called the rafiinate. The lower layer comprising mostof the solvent and naphthenic compounds, is then withdrawn from theraffinate.

. The rafiinate is then heated and treated with steam or an inert gas toremove the small amount of solvent dissolved therein. This treatedrafflnate is clay-treated and may be given subsequent treatments withsulfuric acid in order to obtain good sludge and color stability.Alternatively, the extraction may be carried out in countercurrentmanner by methods well known in the art, in which case it will usuallybe desirable to work at ordinary temperatures or below.

The object of our invention is provide a method separate from the highlyparaflinic oil. The temperature at which this separation is effected iscalled the extraction temperature. In this particular example we use anextraction temperature of about 60 F. It should be understood, however,that the extraction temperature may vary with different oils andsolvent, but generally the extraction temperature is at least 40 F.below the miscibility temperature. Also, the oil may be cooledstep-wise, that is, two or more separations may be made at differenttemperatures.

The solvent containing aluminum chloride and extract, or bottom layer,is withdrawn from the bottom of the agitator, and then the rafflnate isstripped with an inert gas or steam to recover the solvents therefrom.Generally, the stripping is performed at a somewhat elevatedtemperature.

The raffinate or highly parafiinic fraction of the oil may then be claytreated in the ratio of about 300 to 1000 gallons per ton of clay inorder to improve the color of the final product. Fullers earth,bentonite, Attapulgus clay or other suitable decolorizing clay may beused for this purpose.

The first example of the following table discloses the properties of theabove oil when treated in the manner and under the conditionshereinabove set forth. The second example discloses the properties ofthe oil when extracted and treated under the same conditions but in theof extracting mineral oils so as to impart good absence of aluminumchloride.

Table I T 1 Y. M Clay Saybolt sludgling timel'lle C0 01 1e VISCOSl yOUIS Example alter extrac- (per 35??? 3 a tion cent) tori) 210F. F. 10mg. 100mg.

1 13s 69 33a 87 1044 a 88.5 94 129 2 256 67 33s 89 1087 13 88.5 72 112sludge and color stability thereto simultaneously with the step ofsolvent extraction. We have found that a small amount of metal halidessuch as aluminum chloride dissolved and/or colloidally suspended in thesolvent will greatly improve the color and increase the sludge stabilityof the raflinate.

. We will describe our process by extracting a Mid-Continent mixed-baselubricating oil with a single organic solvent containing about 1% ofaluminum chloride dissolved and/or suspended therein. In this particularexample we will use a Mid-Continent lubricating oil distillate having aSaybolt viscosity of 114 at 210 F. and 2350 at 100 F. and a viscosityindex of 56.5, sludging time of less than 10 hours for 10 mg. of sludge.However, it should be understood that our process is applicable to anydistillate or bottom derived from mixed base oils or naphthenic oils.One volume of the oil is mixed in a suitable agitator with 1.5 volumesof beta-beta dichlorethyl ether containing about 1% of aluminumchloride. The mixture is then agitated and heated to a temperaturesomewhat above the miscibility temperature which is about F. In thisparticular example the mixture was heated to F. Generally the solvent orsolvents are miscible with the oil within the range of 50 to 220 F.However, with some solvents the miscibility temperature may be lowerthan this.

After the oil and solvent containing aluminum chloride have been heatedto the miscibility tem perature, the mixture is cooled to a temperaturebelow the miscibility temperature where the solvent containing aluminumchloride and extract From Example 2 of the above table, which gives theresults of the extraction in the absence of aluminum chloride, it willbe noted that the true color of the rafiinate before claying was 256;after claying the true color was 13. The time required for 10 mg. ofsludge to form under the excessive oxidizing conditions was 72 hrs. andthe time required for 100 mg. of sludge to form was 112 hours. Example 1discloses the properties of the oil when treated under exactly the sameconditions but in the presence of 1% by Weight of aluminum chloride. Itwill be observed that the true color of the raffinate after this extraction was 136; after claying the true color was 3-a great improvementover the color obtained in the absence of aluminum chloride. The timerequired for 10 mg. of sludge to form was 94 hrs. and the time requiredfor 100 mg. of sludge to form was 129 hrs.

In view ofthe above table and explanation it is apparent that thepresence of a small amount of aluminum chloride in the solvent greatlydecreases the true color and adds increased sludge stability to the oil.It should be observed that there is no decrease in the yield orviscosity index of the oil in order to obtain this improved color andsludge stability. In fact, it will be noted that a slight increase inyield was obtained. If the above oil is treated with aluminum chlorideper se, about 9%, the sludge stability is very low. In fact, it requiredonly 31 hrs. to form 10 mg. of sludge.

The following table sets forth the properties of the refined oilobtained by the hereinbefore described process when one volume ofdistillate (114 Saybolt viscosity at 210 F., 2350 Saybolt viscosity at100 F. and a viscosity index of 56.5) is extracted with one volume ofthe halogenated ether in the presence of 2% of aluminum chloride byweight at 160 F.

By comparing the properties of the oil set forth in Table II with, theproperties of the oil in Example 2 of Table I it will be observed thatthe true color of the oil after claying are the same, but 1000 gals. ofoil were treated per ton of clay in the case of the oil in Table II andonly 333 gals. were treated per ton of clay in the case of the oil inExample 2 of Table I. It will be noted that the extraction with asolvent in the presence of a small amount of aluminum chloride providesa process of obtaining 1000 gals. of oil of 13 true color per ton ofclay, whereas, in the absence of aluminum chloride only 333 gals. of oilof 13 true color were obtained per ton of clay.

The second example of the following table represents the resultsobtained when one volume of the above oil (Saybolt viscosity of 114 at210 F., 2350 at 100 F. and a viscosity index of 56.5) is treated with 1%volumes of nitrobenzene containing 1% by weight of aluminum chloride.The treating temperature used in this example was 200 F. The firstexample of this table discloses the properties of the above oil whentreat ed under the same conditions with the same VVUI \Ill solvents inthe presence of metallic halides, we may use other organic selectivesolvents. Examples of solvents which may be used in combination withthese metallic chlorides such as aluminum chloride, boron trichlorideand zinc chloride are: methyl 2-chlorethyl ether, di(2-chlorethyl)ether, methyl chloropropyl ether, methyl 2-3 dichloropropylether, ethyl 2-3 dichloropropyl ether. ethyl 2-3 chloropropyl ether,2-chlorethyl propyl ether, dichlorisopropyl ether, dichloropropyl ether,nitrobenzene, nitrotoluene, nitroxylene, ethyl chloracetate, ethyldichloracetate, ethyl chlorpropionate, 2-chlorethyl acetate, methylchloracetate, 2-chlorethyl propionate, sulfur dioxide, dioxane,pyridine. nitronaphthalene, or mixtures of the above. We have found thatthe alpha chlorinated aliphatic ethers and esters are more reactive thanthe beta or gamma halogenated compounds and that satisfactory resultsare not obtained with these alpha halogenated compounds.

Instead of using a single organic solvent in the presence of thesemetallic halides, we may use mixed solvents in combination with aluminumchloride, boron tri-chloride or zinc chloride. Examples of mixedsolvents which may be used for extracting lubricating oils are:

Table IV Acetone and nitrobenzene Acetone and di(2-chlorethyl) etherAcetone and dichlorobenzene Acetone and cresol Methyl ethyl ketone anddi(2-chlorethyl)ether Methyl propyl ketone and nitrobenzene Methylpropyl ketone and di(2-chlorethyl) ether Ethyl acetate and nitrobenzeneEthyl acetate and di 2-chlorethyl)ether Carbon dioxide and sulfurdioxide Propyl ether and nitrobenzene solvent but in the absence ofaluminum chloride. Iso-propyl ether and nitrobenzene Table III SayboltSludging Clav True color meld viscosity t1ruehours treated TrueViscosity Example igfi gg 53 (gals. per color index 210 F. 100 F. 10 mg.100 mg.

From Example 2 of the above table it will be observed that the color andsludge stability of the oil treated in the presence of aluminum chlorideis greatly improved. It is apparent that the presence of a small amountof aluminum chloride materially decreases the true color of the oil andadds increased sludge stability to the oil. Furthermore, it will beobserved that these enhanced properties were obtained without the lossof yield or viscosity index. In fact, the viscosity index of the oilwhich was treated with nitrobenzene containing aluminum chloridedissolvent and/or dispersed therein was slightly better than the oilwhich was extracted with the same solvent but in the absence of aluminumchloride. White oils, or substantially colorless mineral oils can beprepared by our process by repeating the extraction of the oil severaltimes with the solvent and metallic halide. The degree of refining willdetermine the number of extractions. Petroleum naphthas may likewise berefined by our process as'hereinbefore described.

Instead of using the hereinabove mentioned Iso-propyl ether andchlorinated aliphatic ethers Methyl acetate and nitrobenzene Methylacetate and di(2-chlorethyl)ether Propyl acetate and nitrobenzene Ethylpropionate and nitrobenzene Ethyl propionate and di(2-chlorethy1) etherMethyl propionate and nitrobenzene Sulfur dioxide and benzene Sulfurdioxide and dimethyl ether Sulfur dioxide and diethyl ether The metallichalides which have proven most desirable for this process aresubstantially an- IIUL ployed in this specification and claim in ageneric sense to include the compounds that have a low viscosity index,low A. P. I. gravity, and usually rapid sludge-forming characteristics,examples of which are the aromatic, aromatic-like, olefins, highmolecular weight polymethylenes, nitrogen and sulfur compounds.

The term non-sludging and stable to oxidation and sludging is used inthe specification and claim to cover an oil which has greater sludgestability than the parent oil. These terms are not intended to defineoils that are absolutely stable against sludge formation under rigidoxidizing conditions for long periods of time.

In addition to or instead of extracting the lubricating oils in thepresence of aluminum chloride, we may first treat the oil With aluminumchloride and then extract with a selective solvent. However, thisprocedure is usually more expensive for the reason that it requiresadditional operations after the extraction with the solvent. We havefound that the process of extracting in the presence of aluminumchloride is very economical.

The oil treated by our process may be dewaxed before and/or after theextraction, but we prefer to dewax the oil before extraction. While wehave described our invention with reference to specific materials andproportions of solvents, it should be understood that the scope of ourinvention is not limited thereto except insofar as set forth in theappended claim.

We claim:

The method of preparing a non-sludging lubricating oil having a low truecolor from a mineral oil containing naphthenic and paraflinicconstituents, the steps comprising mixing one volume of said mineral oilwith at least one volume of a selective solvent selected from the groupconsisting of di(2-chlorethyl)ether and nitrobenzene which has a smallamount of aluminum chloride dissolved therein, heating said mixture toan elevated temperature to effect substantially complete solution,cooling said admixture to a temperature at which phase separationoccurs, withdrawing the top layer and removing therefrom the dissolvedsolvent.

KENNETH TAYLOR. BERNARD H. SHOEMAKER.

